Product Review – HMF Competition Exhaust System

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HMF Muffler

Breaking Lap Times Without Breaking Banks
by Jason Giacchino

The Reality:

4-stroke exhaust systems can cost a fortune these days! While we love the performance of a modern tuned-up 450, exhaust prices have us occasionally tearing up over the good old days when a complete 2-stroke system could be had for a couple hundred bucks.

The Situation:

We needed a little extra oomph out of our 2009 Kawasaki KFX450 and the time had come to start narrowing down choices in the pipe/muffler department. While there were a few carbon fiber units that tickled our fancy, part of our mission was to find a complete system that came in south of a grand. Well-south of a grand if possible!

The Solution:

HMF’s catalog revealed a complete stainless system for a very budget-friendly 5.95. The system consisted of a one-piece header/mid pipe and a muffler with removable end cap/tuning inserts. Considering this complete system costs what many companies are charging for the muffler (slip-on) alone, we revealed the well-worn credit card and gave it a go.

The Installation:

Fortunately, HMF’s engineers clearly studied the Kawasaki KFX’s dimensions very carefully when developing this pipe. The routing is clean and precise and makes no unwanted contact with the frame, engine or plastic. In fact, it took us a bit longer to remove the beat-up stock system than it did to install the HMF. All of the necessary mounting hardware is included in the kit and mated perfectly with our stock engine. This is a modification perfectly suited to the backyard mechanic/weekend warrior type.

HMF Mounted

The Set-Up:

Yes, we know: Life was simpler back when exhaust systems included a few brass jets that you could slip into the carburetor to make the most of your new set-up. Fuel injection has muddled up those waters a bit, but the good news is HMF has done the legwork for you by coming up with fuel maps that can maximize output precisely as you see fit. The exhaust system includes several recommendations and HMF will gladly get you pointed in the right direction, should you seek something outside of their normal parameters, by just visiting their site. Aside from the exhaust system and requisite fuel map adjustment, our machine was showroom stock.

Another aspect of customization with this particular system works from the removable end cap/tunable inserts mentioned above. Like all facets of performance, there is a give & take relationship at play here: The smallest insert yields the biggest gains, but it is also the barkiest. Going bigger with the inserts lessens the power potential but makes the exhaust quieter as well. Rather than force you into accepting what the factory deems the proper ratio of power/noise, HMF gives the customer the option to run what they see fit.

In our case we opted for the medium sized insert, which provided the right blend of performance with sound output.

The Test:

While we expected a couple horsepower increase by kicking the stocker to the curb and putting on the freer-slowing HMF, we were astounded to note a near 7-horsepower gain on the dyno!

The price point on this system was attractive to begin with, but the dollar per horsepower increase was the icing on the cake. Again the way you wish this power to be delivered is a personal choice, based on the available fuel maps (hit the KFX forums for some really interesting suggestions) but we ended up settling on a map that gave the KFX a bit more pull in the mid and up reaches of the powerband for our high-speed, flowy test track. Were we powering through mud or tight east coast trail conditions, there is little doubt we could configure the settings for optimal low-end snap with just a swap of the map.

The Conclusion:

We are just enamored with this exhaust system. The price was reasonable, installation a breeze, performance gains appreciable, and perhaps best of all, the customer gets some solid customization options to work with. The tunable inserts really do make a difference both in terms of delivery and sound output and it’s really nice to know the choice to run the louder competition settings is left up to the consumer and their particular needs on a given day.

HMF actually does make their own fuel injector optimizer available on their site, but we found that any map computer is perfectly adequate for making maximum use of the exhaust system (in our case we used a Power Commander).

HMF makes dozens of combinations for just about every make and model, so to follow our exact route: Kawasaki KFX 08-10 Competition Series/Full System. If the option of the interchangeable end caps isn’t necessary for you, the Performance Series (with brushed finished) can be had for an even more affordable 5.95.

The Contact:

www.hmfracing.com

 

 

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